A moving body such as a motor vehicle is equipped with various electronic devices. Therefore, in order to supply electric power from a power source and a control signal from a computer to these electronic devices, a wire harness 100 is arranged in the motor vehicle. The wire harness includes plural electric wires 106 (FIG. 10) and connectors attached to the ends thereof.
The electric wire 106 is composed of a conductive core 105 (FIG. 10) and a cladding which is made of insulating synthetic resin and clads the core 105. The electric wire 106 is a “clad-wire”. The electric wire 106 has been manufactured by a manufacturing apparatus 100 shown in FIG. 10. The manufacturing device illustrated in FIG. 10 includes a supply unit 101, an extrusion cladding unit 102, a cooling water bath 103 and a take-up unit 104.
In manufacturing the electric wire 106, the wire manufacturing device 100 sequentially shifts the core 105 or electric wire 106 to the supply unit 101, extrusion cladding unit 102, cooling water bath 103 and take-up unit 104. In order to shift the core 105 or electric wire 106, the wire manufacturing device 100 is provided with plural pulleys 107.
The supply unit 101 supplies the core 105 with no cladding. The extrusion cladding unit 102 extrudes the insulating synthetic resin to the periphery of the core 105 to form the cladding. The cladding water bath 103 cools the cladding which clads the core 105 with the aid of the extrusion cladding unit 102. The take-up unit 104 cuts the electric wire 106 composed of the core 105 and cladding into segments each having a prescribed length and wind them around a drum so that they are in a shipping state. Thus, the electric wire 106 is manufactured by the electric wire manufacturing apparatus 100.
The connector is composed of a conductive terminal metal fitting and a connector housing. The terminal metal fitting is attached to the end of the electric wire 106 and electrically connected to the core 105 thereof. The connector housing is formed in a box shape to accommodate the terminal metal fitting.
In assembling the wire harness, the electric wire 106 is cut into wire segments (referred to electric wires 106) each having a prescribed length. Metal fittings are attached to the ends of the wire segments. Thereafter, the terminal metal fittings are inserted into the connector housing. Thus, the wire harness is assembled.
The electric wires 106 must be distinguished in terms of the size of the core 105, substance of the cladding (presence or absence of heat-resistance) and using object. The using object is a system of a motor vehicle in which the electric wires are used, such as an air bag, ABS (Antilock Brake System), a system for supplying a control signal such as a vehicle speed and a power transmission system.
The electric wires are colored with various colors and bear markings in order to identify the using object. For this purpose, in the conventional wire manufacturing device 100 illustrated in FIG. 10, the extrusion cladding unit 102 mixes a coloring agent into the synthetic resin for the cladding. The synthetic resin and coloring agent are mixed to color the synthetic resin with the same color as the coloring agent.
The synthetic resin is extruded to the periphery of the core 105. Thus, the cladding or electric wire 106 is colored.
On the other hand, a variety of demands have been made for the motor vehicle from a user. Therefore, it has been demanded that the motor vehicle is equipped with a variety of electronic devices. Thus, as the case may be, one hundred kinds of electric wires are used for the wire harness. In this case, the electric wires 106 with a wide variety of colors are used. For this reason, the wire manufacturing device 100 is demanded to be able to change the color of the cladding.
The wire manufacturing apparatus 100 illustrated in FIG. 10, in order to change the color of the cladding (i.e. electric wire 106), the extrusion cladding unit 102 was temporarily stopped to change the coloring agent to be mixed into the synthetic resin. In this case, in order to manufacture a wide variety of electric wires with a wide variety of colors, the extrusion cladding unit 102 must be stopped frequently. This reduced the manufacturing efficiency of the electric wires 106.
In order to obviate such inconvenience, it has been proposed to change the coloring agent to be mixed into the synthetic resin while the extrusion cladding unit 102 is driven. In this case, immediately after the coloring agent has been changed, both coloring agents before and after changing are mixed into the synthetic resin so that the cladding is colored with the mixed color. Since the mixed color of the electric wire 106 is not the color corresponding to the above system, the electric wire 106 cannot be used fro the wire harness.
Thus, if the coloring agent to be mixed into the synthetic resin is changed while the extrusion cladding unit 102 is driven, the electric wire involves a portion which cannot be used for the wire harness. This led to a tendency of decreasing the of material yield of the electric wire 106.
In order to suppress the wasteful portion of the electric wire 106, i.e. suppress the material yield of the electric wire 106, in e.g. JP-A-6-150774, it is proposed to apply the liquid color ink with the same color as that of the coloring agent after changing onto the mixed area of the color agents. In this case, if the mixed color (referred to as a base color) and the coloring agent after changing are different in their hue, or the brightness of the base color is lower than that of the coloring agent after changing, the base color might be seen through the liquid color ink. In addition, in this case, the liquid color ink is applied to the cladding after formed, the liquid color ink is apt to come off from the outer surface of the cladding.
In this way, in the technique described in JP-A-6-150774, the color of the liquid color ink must be determined according to the base color. This made it difficult to change the color agent from a dark coloring agent to a bright coloring agent. Thus, the technique described in JP-A-6-150774 has a limitation in changing the coloring agent that the coloring agent must be changed into the coloring agent with lower brightness.
Further, in the conventional wire manufacturing apparatus 100, in the extrusion cladding, the coloring agent is mixed into the synthetic resin constituting the cladding. The cladding is colored at the same time as the core is coated with the cladding. Accordingly, the electric wire 106 used for the motor vehicle has about one hundred kinds of product numbers in terms of the color of the outer surface (the electric wire 106 has a vast number of product numbers inclusive of those with different wire diameters).
Thus, a wire manufacturer or wire harness manufacturer must store about one hundred electric wires with different colors of the outer surface temporarily or for a long period. Therefore, a large space is required to store the electric wires and a troublesome work is necessary to manage the product numbers of the electric wires 106.
Accordingly, a first object of this invention is to provide a method and apparatus for manufacturing an electric wire which can change the color for coloring the electric wire and electric wire itself. A second object of this invention is to provide an electric wire in which the coloring color is difficult to come off.